Conventional art has a problem that, when an object is recognized via an imaging device, performance of recognition is not high, since lighting condition varies in wide rage under natural environmental light. By using artificial light, performance of recognition is improved, the influence by the natural environmental light, especially the sunshine, is still required to be eliminated.
Japanese patent application publication No. 2006-155422 describes that an image is generated and recognized by differentiation between an output of a light detector when a light source does not illuminate a subject space and an output of the light detector when the light recourse illuminates the subject space.
U.S. Pat. No. 6,239,456 describes that a light source emits a pulse of light, and, charge generated by a light incident from a view is split into plural capacitors connected via split gates to photo diodes in synchronous with the emission of the light. It is also described that signal processing is applied to this charge stored in the plural capacities, output waveforms corresponding to the pulse emission of the light source is extracted, and a distance up to a subject is measured based on the phase differentiation among the output waveforms.
A quantity of charge sampled at one time will be significantly decreased as a ratio of light emission is increased. If a light incident has a non-uniform peak, especially if such peak is located close the split gate, the quantity of charge is changed in accordance with the capacitor to which the charge transferred by the split gate.
Japanese patent application publication No. H02-304974 describes the structure and the manufacturing method of a buried photo diode. On the N type region 6 (FIG. 1(e)) of the photo diode on the substrate, the P type region 13 is formed, and the N type photo diode 6 is buried (FIG. 1(f). The electric charge generated in the photo diode 6 is, by means of the silicon gate as a transfer gate, transferred to N type region 7 as an electric charge transfer portion.    Document No. 1: Japanese Published Patent Application 2006-155422    Document No. 2: U.S. Pat. No. 6,239,456    Document No. 3: Japanese Published Patent Application H02-304974